Airships are lighter than air aircraft whose lifting is mainly due to static impulse of air.
Basically there are two types of airships: balloons, which are not self-propelled that can be displaced due to external impulsion the air currents, and captive balloons that do not move freely, being permanently fastened to the ground. Airships (dirigibles) are vehicles with self-propulsion that are usually performed by motor drivers.
In the case of captive balloons, the mooring device for these airships is of great importance, since it enables the captive balloons to efficiently perform their duties, as well as retrieve the airship as needed.
In general, mooring systems have a winch, a safety cable and a safety cable control system that aims to make it impossible for this to contact improper parts of the winch, which would cause cable abrasion. The safety cable control system is also responsible for maintaining the radius of curvature of the cable within acceptable limits, and avoiding excessively sharp bends that may cause wear and break of internal elements such as fiber optic.
The existing winches in the state of the art are generally made for automotive or nautical applications. In these applications, the position of the vehicle being towed or “winched” is known. The vehicle is behind the tug and the cable output direction varies within a narrow range of angles.
In the case of airships, the cable output direction varies substantially in a large opening cone. That is, the airship can be in any direction, since its stabilization is passive. That is, it will always be oriented in the wind direction and course. There is also a ratio between horizontal displacement versus height (called blow-by) that also depends on the magnitude of the wind, the cable section diameter, atmospheric turbulence and net thrust (thrust generated by the gas minus deadweight, minus weight of the payload). That is, the winch operating condition is completely different from the usual uses, whether it is automotive, nautical or for cargo lift.
The problem is exacerbated when using electro-mechanical (MS) or electro-optical-mechanical (EOM) cables, which require an elevated minimum curvature radius to preserve the life of the cable, avoiding the rupture of its core.
The patent literature describes both airships and their mooring systems. The document CN 101898633 discloses a mooring device in a trailer for small and medium-sized airships, provided with a mooring tower. A semitrailer, a turning platform fixed on the semi-trailer by means of a swivel bracket, and a mooring tower positioned in front of a turning platform are disclosed. A plurality of horizontal support arms positioned on the rear of the platform and a box of capsules are also arranged at the rear of the turning platform. Although useful, this mooring device has a large size and serves to store the empty airship.
The U.S. Pat. No. 4,842,219 anticipates a fastening system for luminous signs during launch, which has a mooring device. The mooring device is provided with one degree of freedom that allows it to turn around the vertical axis, and a tilt up and down, to try to control safety cable tension avoiding his break. This mooring device, however, is not able to turn vertically.
The patent PT103489 anticipates a control system for releasing and retrieving the safety cable of an airship capable of converting the wind in wind energy.
The US patent application US20120181381 deals with a mooring device for an airship, which allows maintaining a minimum curvature radius of the cable, and which is provided with a rigid structure that serves for the safety cable routing. However, since the structure is rigid, which means that the cable exerts a considerable normal force over this structure, the structure is made of metal. The friction of the cable in the structure must be considerably large, which is disadvantageous, and also creates structural requirements relevant to the cable guide structure.
The prior art therefore anticipates different ways of controlling the stress and routing of airships safety cables.